I. Field of the Invention
This invention relates to a system and method of providing access to the interior of a branch pipeline, referred to as a “cross-line” that intersects with a main pipeline of equal or greater diameter.
II. Description of the Prior Art
Pipelines are used in all parts of the world for the transportation of hydrocarbon products including primarily natural gas and crude oil. These commodities are exceedingly valuable and, in fact, indispensable to the modern standard of living enjoyed throughout the world. However, in addition to being valuable, they are also hazardous. Such hazards include danger to life as can be a consequence of explosions or fires from leaked oil or gas products and, in addition, these products can be harmful to the environment. For these reasons, it is important that pipelines be periodically inspected and/or evaluated for proper repair and maintenance. Pipelines are usually buried under the earth's surface to protect them against hazards that would exist if they were laid on the earth's surface. In addition, due to the increased amount of offshore oil and gas exploration, many pipelines today are laid at the bottom of an ocean, that is, on the ocean floor. For these reasons, the exterior surfaces of pipelines are not readily available for visual inspection. As a consequence, the most economical and effective way of inspecting pipelines is by transmitting pigs that are moved through the pipelines by fluid flow, that is, by the flow of natural gas or crude oil. For background information as to the application and use of pipeline pigs, reference may be had to an article entitled “Fundamentals of Pipeline Pigging”, authored by Burt VerNooy, appearing in Pipeline Industry, September/October 1980, published by the Gulf Publishing Company of Houston, Tex.
A particular problem is encountered with the use of pipeline pigs for inspecting cross-lines, that is, pipelines that interconnect between other and usually, larger diameter pipelines. While primary pipelines may extend for miles or even hundreds of miles, cross-lines are typically of much shorter length, such as a few hundred feet up to a few miles. It is sometimes difficult and always expensive to install pig launching and receiving facilities for such cross-lines.
The term “cross-line” as used herein includes a pipeline that interconnects between other pipelines, as above stated, and also branch lines, that is, a smaller diameter pipeline that extends from a main pipeline that does not necessarily connect to another main pipeline but that connects such as to a storage facility, a processing plant or the like. Thus, “cross-lines” herein includes branch lines.
For additional background information relating to this invention, reference may be had to the following previously issued United States patents.
U.S. Pat. No.InventorTitle  408,826ConroyCross For Gas Mains or Pipes1,825,034Weatherhead, Jr.Sectional Pipe Coupling2,546,502HarringtonMeans For IncorporatingSolid Fat In Liquid Fatty Mixtures2,563,244HolicerFluid Control Mechanism2,913,259RingsSidebranch Fitting For MainSupply Pipe3,135,278Foord et al.Loading Pipeline PiggingSystem and Method3,373,452WattsManifold Assembly For Hot andCold Water Faucet Pairs ArrangedBack to Back3,510,156MarkowzDevice For Transmitting Flows3,766,947OsburnFluid Tight Closure4,579,484SullivanUnderwater Tapping Machine4,708,372Arima et al.Cross Piping Construction4,880,028Osburn et al.Completion Machine5,439,331Andrew et al.High Pressure Tapping Apparatus5,678,865AndersonTank Tee Unit5,967,168Kitani et al.Method of Connecting Branch Pipe6,196,256KlampferManifold